INS and Insulin resistance: A recent study using a distinct Irp2−/− mouse strain reported that 18-month-old male Irp2−/− mice displayed hyperglycemia, insulin resistance as determined by ITTs, and no change in early-phase glucose-stimulated insulin secretion47, while we found that 18-month-old male Irp2−/− mice displayed reduced pancreatic insulin content and glucose-stimulated insulin secretion compared with WT mice.